Drug-bedeviled actor Robert Downey Jr. was booted off “Ally McBeal” show yesterday – hours after being busted on new misdemeanor narcotics charges.

In a repeat performance of his sad, fallen-off-the-wagon act, Downey was found strung out and stumbling into an alley at about 12:10 a.m., Culver City, Calif., police said.

Cops picked up Downey, 36, as he walked on Washington Boulevard. He was jailed and then released to his parole officer after posting $2,500 bail, according to arrest records.

“One of our patrol officers observed him and began an investigation after seeing him in an alley,” Culver City police Lt. Dave Tankenson said. “During the investigation, the officer determined that [Downey] was showing symptoms of being under the influence of a controlled substance.”

Cops gave Downey a urine test, but did not say what illegal substance the test turned up. The actor has voluntarily checked himself into rehab.

News of the reported relapse was apparently the final straw for “McBeal” producer David Kelley – a strong supporter of Downey in the past.

“We are wrapping up the stories on the final few episodes of ‘Ally McBeal’ for the season without him,” Kelley said in a statement.

The actor won a Golden Globe for his portrayal of star Calista Flockhart’s love interest on the Fox TV show.

Downey spokesman Alan Nierob said the actor is now “in charge of his own destiny.”

In a prepared statement, Downey’s lawyers said their client is fighting an uphill battle against addiction.

“Like thousands of others, Mr. Downey continues to struggle with his disease on a daily basis,” said Downey defense lawyer Daniel Brookman. “He remains committed to combating this disease and taking the necessary steps to do so.”

The arrest forced Downey to cancel an appearance with “Ally” singer Vonda Shepard last night and it complicates his already sticky legal standing.

Cops in Palm Springs busted into Downey’s posh resort room on Nov. 25, and prosecutors charged him with felony possession of cocaine and Valium and a misdemeanor count of being under the influence.

Downey is scheduled to appear Monday before a Riverside County judge to face charges from a Nov. 25 bust in Palm Springs, but his prosecutor said that court date might be postponed.